Showing papers on "Wideband published in 2013"
TL;DR: In this article, various wideband spectrum sensing algorithms are presented, together with a discussion of the pros and cons of each algorithm and the challenging issues, and special attention is paid to the use of sub-Nyquist techniques, including compressive sensing and multichannel sub- Nyquist sampling.
Abstract: Cognitive radio has emerged as one of the most promising candidate solutions to improve spectrum utilization in next generation cellular networks. A crucial requirement for future cognitive radio networks is wideband spectrum sensing: secondary users reliably detect spectral opportunities across a wide frequency range. In this article, various wideband spectrum sensing algorithms are presented, together with a discussion of the pros and cons of each algorithm and the challenging issues. Special attention is paid to the use of sub-Nyquist techniques, including compressive sensing and multichannel sub- Nyquist sampling techniques.
536 citations
TL;DR: In this article, a tightly coupled dipole array with an integrated balun (TCDA-IB) is developed which achieves 7.35:1 bandwidth (0.68 - 5.0 GHz) while scanning to ±45° in all directions, subject to.
Abstract: A key challenge in the design of wideband dipole phased arrays is the design of equally wideband baluns which are sufficiently compact to fit within the unit cell (typically in the linear dimension at low frequencies). In this paper, we exploit the reactance of a compact Marchand balun as an impedance matching network for each array element. The elimination of bulky external baluns results in a significant reduction of size, weight and cost, while the bandwidth is simultaneously improved by over 30%, compared to standard feeding techniques. In this manner, a tightly coupled dipole array with an integrated balun (TCDA-IB) is developed which achieves 7.35:1 bandwidth (0.68 - 5.0 GHz) while scanning to ±45° in all directions, subject to . In a dual-polarization configuration, the TCDA-IB has low cross polarization of over the majority of the band. Measured results are presented for a prototype 8 × 8 element TCDA-IB, showing good agreement with simulation.
304 citations
TL;DR: Recent new methods in wideband signal processors including high-resolution, arbitrary response, low noise, programmable processing, beamforming, and ultra-wide continuous filter tunability, are presented.
Abstract: Photonic signal processing offers the advantages of large time-bandwidth capabilities to overcome inherent electronic limitations. In-fibre signal processors are inherently compatible with fibre optic microwave systems that can integrate with wireless antennas, and can provide connectivity with in-built signal conditioning and electromagnetic interference immunity. Recent methods in wideband and adaptive signal processing, which address the challenge of realising programmable microwave photonic phase shifters and true-time delay elements for phased array beamforming; ultra-wideband Hilbert transformers; single passband, widely tunable, and switchable microwave photonic filters; and ultra-wideband microwave photonic mixers, are described. In addition, a new microwave photonic mixer structure is presented, which is based on using the inherent frequency selectivity of the stimulated Brillouin scattering loss spectrum to suppress the carrier of a dual-phase modulated optical signal. Results for the new microwave photonic mixer demonstrate an extremely wide bandwidth operation of 0.2 to 20 GHz and a large conversion efficiency improvement compared to the conventional microwave photonic mixer.
301 citations
TL;DR: In this article, a fully electronically reconfigurable 400-element transmitarray is studied numerically and experimentally in the X-band, where two p-i-n diodes are integrated on the active side of each cell to control its transmission phase.
Abstract: A fully electronically reconfigurable 400-element transmitarray is studied numerically and experimentally in X-band. The array operates in linear polarization and consists of 20 × 20 unit-cells. A 1-bit phase resolution has been selected for the unit-cell in order to reduce the complexity of the biasing network and steering logic, the insertion loss and the overall cost of the antenna system. The unit-cell stack-up is simple and is made of four metal layers: active side, biasing lines, ground plane and passive side. Two p-i-n diodes are integrated on the active side of each cell in order to control its transmission phase. The active array contains 800 diodes in total. It demonstrates experimentally pencil beam scanning over a 140 × 80-degree window over a 15.8% fractional bandwidth, with a maximum gain of 22.7 dBi at broadside. We also show that the same antenna array can be used for beam shaping applications (flat-top beam). The experimental results presented between 8 and 12 GHz are in good agreement with the theoretical performance calculated using full-wave electromagnetic simulations and an in-house CAD tool based on analytical modeling.
248 citations
TL;DR: In this paper, a new type of microresonators enabled by micromachining of ion sliced X -cut LiNbO3 thin films is reported, which has a high electromechanical coupling (kt2) of 11.5%.
Abstract: This paper reports on a new type of microresonators enabled by micromachining of ion sliced X -cut LiNbO3 thin films. In operation, the device is excited into lateral vibrations, thus allowing the center frequency to be determined by the lithographically defined dimensions of the excitation electrodes. The demonstrated device has a high electromechanical coupling (kt2) of 11.5%-the highest attained for laterally vibrating microelectromechanical systems resonators. Device orientation was also varied to investigate its impact on kt2 and experimental data have shown good agreement with theoretical predictions. Several key performance parameters, including the quality factor (Q), the static capacitance, C0 , the temperature coefficient of frequency (TCF), and the power handling, are also characterized and the related experimental data are presented. The devices demonstrate Q 's up to 1800. The measured TCFs range from -55 to -69 ppm/K and can be considered sufficiently low for wideband RF filtering. The high electromechanical coupling and the high Q of this new class of devices show promise for the implementation of multifrequency wideband multiplexers and filter banks for reconfigurable RF front-ends.
245 citations
TL;DR: In this article, a closed-loop echo cancellation technique is proposed to cancel high-power echoes at the receive chain as echoes with powers much higher than the desired received signal, which can be implemented purely in the analogue domain.
Abstract: Full Duplex or Simultaneous transmission and reception (STR) in the same frequency at the same time can potentially double the physical layer capacity. However, high power transmit signal will appear at receive chain as echoes with powers much higher than the desired received signal. Therefore, in order to achieve the potential gain, it is imperative to cancel these echoes. As these high power echoes can saturate low noise amplifier (LNA) and also digital domain echo cancellation requires unrealistically high resolution analog-to-digital converter (ADC), the echoes should be cancelled or suppressed sufficiently before LNA. In this paper we present a closed-loop echo cancellation technique which can be implemented purely in analogue domain. The advantages of our method are multiple-fold: it is robust to phase noise, does not require additional set of antennas, can be applied to wideband signals and the performance is irrelevant to radio frequency (RF) impairments in transmit chain. Next, we study a few protocols for STR systems in carrier sense multiple access (CSMA) network and investigate MAC level throughput with realistic assumptions in both single cell and multiple cells. We show that STR can reduce hidden node problem in CSMA network and produce gains of up to 279% in maximum throughput in such networks. Moreover, at high traffic load, the gain of STR system can be tremendously large since the throughput of non-STR system is close to zero at heavy traffic due to severe collisions. Finally, we investigate the application of STR in cellular systems and study two new unique interferences introduced to the system due to STR, namely BS-BS interference and UE-UE interference. We show that these two new interferences will hugely degrade system performance if not treated appropriately. We propose novel methods to reduce both interferences and investigate the performances in system level. We show that BS-BS interference can be suppressed sufficiently enough to be less than thermal noise power, and with favorable UE-UE channel model, capacities close to double are observed both in downlink (DL) and uplink (UL). When UE-UE interference is larger than DL co-channel interferences, we propose a simple and "non-cooperative" technique in order to reduce UE-UE interference.
208 citations
TL;DR: In this article, a L-probe patch antenna array using multilayer low temperature co-fired ceramic (LTCC) technology is presented for 60 GHz band applications. The proposed antenna array is designed with a high gain in the impedance bandwidth by introducing a novel soft-surface structure.
Abstract: A 4 $\,\times\,$ 4 L-probe patch antenna array using multilayer low temperature co-fired ceramic (LTCC) technology is presented for 60-GHz band applications. The proposed antenna array is designed with a high gain in the impedance bandwidth by introducing a novel soft-surface structure. The soft-surface structure comprised of metal strips and via fences reduces the losses caused by severe surface waves and mutual coupling between adjacent elements to improve the radiation performance. The proposed antenna array is convenient for integrated applications. The fabricated antenna array excluding the measurement transition has dimension of 14.4 $\,\times\,$ 14.4 $\,\times\,$ 1 mm $^{3}$ . The simulated and measured impedance and radiation performance are studied and compared. Good agreement is achieved between simulation and measurement. The proposed antenna array shows a wide simulated impedance of 29% from 53 GHz to 71 GHz for $\vert {S}_{11}\vert dB, measured broadband 3-dB gain bandwidth of 18.3% from 54.5 GHz to 65.5 GHz and the gain up to 17.5 dBi at 60 GHz, respectively.
162 citations
TL;DR: The gyro-BWO generated a maximum output power of 12 kW when driven by a 40 kV, 1.5 A, annular-shaped large-orbit electron beam and achieved a frequency tuning band of 88-102 by adjusting the cavity magnetic field.
Abstract: Experimental results are presented of the first successful gyrotron backward wave oscillator (gyro-BWO) with continuous frequency tuning near the low-terahertz region. A helically corrugated interaction region was used to allow efficient interaction over a wide frequency band at the second harmonic of the electron cyclotron frequency without parasitic output. The gyro-BWO generated a maximum output power of 12 kW when driven by a 40 kV, 1.5 A, annular-shaped large-orbit electron beam and achieved a frequency tuning band of 88-102.5 GHz by adjusting the cavity magnetic field. The performance of the gyro-BWO is consistent with 3D particle-in-cell numerical simulations.
148 citations
TL;DR: The first in-band diode-pumped TDFAs operating in the 2 µm wavelength region are presented and their suitability as high performance amplifiers in potential future telecommunication networks is tested.
Abstract: We present the first in-band diode-pumped TDFAs operating in the 2µm wavelength region and test their suitability as high performance amplifiers in potential future telecommunication networks. We demonstrate amplification over a 240nm wide window in the range 1810 - 2050nm with up to 36dB gain and noise figure as low as 4.5dB.
146 citations
TL;DR: In this article, a 60 GHz wideband circularly polarized (CP) U-slot patch antenna array of 4 × 4 elements on low temperature co-fired ceramic (LTCC) is presented.
Abstract: This communication presents a 60-GHz wideband circularly polarized (CP) U-slot patch antenna array of 4 × 4 elements on low temperature cofired ceramic (LTCC). A CP U-slot patch antenna is used as the array element to enhance the impedance bandwidth and a stripline sequential rotation feeding scheme is applied to achieve wide axial ratio (AR) bandwidth. Meanwhile, a grounded coplanar waveguide (GCPW) to stripline transition is designed for probe station measurement. The fabricated antenna array has a dimension of 14 ×16 × 1.1 mm3 . The simulated and measured impedance bandwidths, AR bandwidths, and radiation patterns are investigated and compared. Measured results show that the proposed antenna array has a wide impedance bandwidth from 50.5 GHz to 67 GHz for |S11| <; -10 dB, and a wide AR bandwidth from 54 GHz to 65.5 GHz for AR <; 3 dB. In addition, it exhibits a peak gain of 16 dBi and a beam-shaped pattern with 3-dB beam width of 20°. Moreover, its AR keeps below 3 dB within the 3-dB beam width.
141 citations
TL;DR: In this paper, a buckled spring-mass architecture is proposed to convert the energy of the dynamic mass to electrical energy in the piezoelectric materials as efficiently as possible.
Abstract: Bistable vibration energy harvesters are attracting more and more interest because of their capability to scavenge energy over a large frequency band. The bistable effect is usually based on magnetic interaction or buckled beams. This paper presents a novel architecture based on amplified piezoelectric structures. This buckled spring‐mass architecture allows the energy of the dynamic mass to be converted into electrical energy in the piezoelectric materials as efficiently as possible. Modeling and design are performed and a normalized expression of the harvester behavior is given. Chirp and band-limited noise excitations are used to evaluate the proposed harvester’s performances. Simulation and experimental results are in good agreement. A method of using a spectrum plot for investigating the interwell motion is presented. The effect of the electric load impedance matching strategy is also studied. Results and comparisons with the literature show that the proposed device combines a large bandwidth and a high power density. (Some figures may appear in colour only in the online journal)
TL;DR: In this paper, a comparative analysis of various reconfigurable and multiband antenna concepts is presented, which can be classified into three basic approaches: tunable/switchable antenna integration with radio-frequency switching devices, wideband or multiband antennas integration with tunable filters, and array architectures with the same aperture utilized for different operational modes.
Abstract: A comparative analysis of various reconfigurable andmultiband antenna concepts is presented. In order to satisfy the requirements for the advanced systems used in modern wireless and radar applications, different multiband and reconfigurable antennas have been proposed and investigated in the past years. In this paper, these design concepts have been classified into three basic approaches: tunable/switchable antenna integration with radio-frequency switching devices, wideband or multiband antenna integration with tunable filters, and array architectures with the same aperture utilized for different operational modes. Examples of each design approach are discussed along with their inherent benefits and challenges.
TL;DR: In this article, a CPW slot loop fed Minkowski shaped fractal dielectric resonator antenna is proposed to bring higher order modes close together to realize a wide impedance bandwidth.
Abstract: A CPW slot loop fed Minkowski shaped fractal dielectric resonator antenna is proposed. Self similar property of fractal geometry is utilized to bring higher order modes close together to realize a wide impedance bandwidth. A comparative study of the resonant frequency behavior between the well established fractal electrical boundary antennas and fractal magnetic boundary antennas is presented to provide insight into the functionality of the proposed antenna. The comparison highlights the fact that electrical boundary lowers resonance frequency, whereas fractal magnetic boundary increases the resonant frequency. Minkowski fractal is also compared with Koch fractal and Sierpinski curve geometries. It is observed that the Minkowski fractal DRA yields the widest impedance bandwidth along with stable gain amongst the three proposed geometries. The proposed antenna exhibits a fractional bandwidth of 64% (5.52 -10.72 GHz) and a maximum gain of 4.9 dBi.
TL;DR: In this paper, a stub-loaded ring resonator is presented as a novel wideband bandpass power divider with good in-band responses and out-of-band harmonic suppression.
Abstract: A simple stub-loaded ring resonator is presented as a novel wideband bandpass power divider with good in-band responses and out-of-band harmonic suppression. The first two resonances of the ring resonator are excited and employed to construct a wideband passband. By adjusting the length of loaded open stubs, four transmission zeros can be generated in the lower and upper stopbands. After installing three coupled-line sections at one input port and two output ports along the ring, additional two in-band poles and one upper-stopband transmission zero are further introduced. Subsequently, total five transmission zeros are utilized to improve the passband selectivity and suppress the high-order harmonic. In addition, a single resistor is properly placed between two output ports to ensure the isolation. Finally, a prototype power divider is fabricated and verified experimentally with attractive bandpass features.
TL;DR: This paper proposes a sensing scheme based on a sub-Nyquist sampling method called multicoset sampling, which is similar to the polyphase implementation of the Nyquist sampling, but requires less A/D converters.
Abstract: In this paper, we consider the problem of locating multiple active spectrum subbands in a wide range of frequency bands. A major challenge associated with such wideband spectrum sensing is that it is either infeasible or too expensive to perform Nyquist sampling on the wideband signal. In this paper, we propose a sensing scheme based on a sub-Nyquist sampling method called multicoset sampling, which is similar to the polyphase implementation of the Nyquist sampling, but requires less A/D converters. In contrast to the traditional sub-Nquist approaches where the wideband signal is first reconstructed from the sub-Nyquist samples, we develop a method that directly estimates the power spectrum of the wideband signal of interest using the sub-Nyquist samples, by exploiting its statistical properties. We also characterize the statistical distribution of the proposed power spectrum estimator, based on which we obtain a constant-false-alarm energy detector for the frequency bins. Simulation results are provided to demonstrate the effectiveness of the proposed multiband spectrum sensing method based on sub-Nyquist sampling.
TL;DR: In this paper, a microstrip-fed monopole mounted on an artificial magnetic conductor is demonstrated to improve the gain by 5 dB over previous works and exhibit much wider impedance bandwidth while maintaining a thin antenna profile and a 20% electrical size reduction.
Abstract: Significant gain and bandwidth improvement of inkjet-printed antennas with integrated artificial magnetic conductor (AMC) is achieved by utilizing wideband ground-backed frequency selective surfaces (FSSs) to overcome the high losses of organic substrates such as paper. A microstrip-fed monopole mounted on an artificial magnetic conductor is demonstrated to improve the gain by 5 dB over previous works and exhibit much wider impedance bandwidth while maintaining a thin antenna profile and a 20% electrical size reduction. The effect of AMC bandwidth on substrate losses and the gain reduction caused by finite AMC array effects are investigated in an effort to produce high-gain, miniaturized, low-cost wearable and structure mount antennas.
TL;DR: In this article, the authors present a linear multi-harmonic analysis method to evaluate the performance of digitally controlled dual RF-input power amplifiers (PAs) in a complex design space involving two independent inputs.
Abstract: This paper presents a linear multi-harmonic analysis method to evaluate the performance of digitally controlled dual RF-input power amplifiers (PAs). The method enables, due to its low computational cost, optimization of PA efficiency and bandwidth in a complex design space involving two independent inputs. Under the idealized assumption of short-circuited higher harmonics, the analysis is used to prove the existence of a Doherty-outphasing continuum, featuring high average efficiency over 100% fractional bandwidth. With this result as a foundation, a combiner incorporating microwave transistor parasitics is analyzed without assuming short-circuited higher harmonics, showing that high average efficiencies are also achievable under more realistic conditions. A PA is straightforwardly designed from these calculation results using two 15-W GaN HEMTs. The simulated layout-ready (large-signal transistor model) PA average drain efficiency exceeds 50% over 1.1-3.7 GHz for a 6.7-dB peak-to-average power-ratio WCDMA signal. The measured PA has a maximum output power of 44 ±0.9 dBm and a 6-dB output power back-off (OPBO) power-added efficiency (PAE) of 45% over 1-3 GHz. After applying digital pre-distortion, excellent linearity is demonstrated when transmitting the WCDMA signal, resulting in an adjacent channel leakage power ratio lower than -57 dBc with corresponding average PAE of 50% and 40% at 1.2 and 2.3 GHz, respectively. This is, to the authors' knowledge, the most wideband OPBO efficiency enhanced PA reported to date, proving the effectiveness of employing linear multi-harmonic analysis in dual-input PA design.
TL;DR: In this article, a quadruple-ridged flared horn achieving almost constant beamwidth over 6:1 bandwidth is presented, which is the first demonstration of a wideband feed for radio telescopes which is capable of accommodating different reflector antenna optics.
Abstract: A circular quadruple-ridged flared horn achieving almost-constant beamwidth over 6:1 bandwidth is presented. This horn is the first demonstration of a wideband feed for radio telescopes which is capable of accommodating different reflector antenna optics, maintains almost constant gain and has excellent match. Measurements of stand-alone horn performance reveal excellent return loss performance as well as stable radiation patterns over 6:1 frequency range. Physical optics calculations predict an average of 69% aperture efficiency and 13 K antenna noise temperature with the horn installed on a radio telescope.
TL;DR: In this article, dual-band and wideband designs of dual-polarized cylindrical dielectric resonator antennas (DRAs) are investigated for DCS (1.71-1.88 GHz) and WLAN (2.4-2.48 GHz) bands.
Abstract: This letter investigates dual-band and wideband designs of dual-polarized cylindrical dielectric resonator antennas (DRAs). These designs make use of the fundamental HEM111 mode and higher-order HEM113 mode of the DRA. The strip- and slot-fed excitation methods are used for Ports 1 and 2 of the antennas, respectively. For demonstration, a dual-band dual-polarized DRA for DCS (1.71-1.88 GHz) and WLAN (2.4-2.48 GHz) bands and a wideband version that covers the 2.4-GHz WLAN band were designed. The S-parameters, radiation patterns, antenna gains, antenna efficiencies, and envelope correlations of the two designs are studied. It was found that the dual-band and wideband designs have port isolations of higher than 36 and 37 dB, respectively. Good agreement between the measured and simulated results is observed.
TL;DR: In this paper, a wideband printed dual-antenna system for mobile terminals is presented, consisting of two symmetric antenna elements and a neutralization line (NL) is printed on a printed circuit board.
Abstract: A wideband printed dual-antenna system for mobile terminals is presented. The dual-antenna, consisted of two symmetric antenna elements and a neutralization line (NL), is printed on a printed circuit board. The antenna element is an F-like monopole with a grounded branch. The working mechanism of the dual-antenna is analyzed based on the S-parameters and the surface current distributions. A prototype shows the measured -10-dB impedance bandwidth is 1.09 GHz (1.67-2.76 GHz) and the measured mutual coupling is lower than -15 dB at the 1.7-2.76-GHz bands. It covers the GSM1800, GSM1900, UMTS, LTE2300, LTE2500, and 2.4-GHz WLAN bands. The radiation patterns are measured, and the diversity performance is evaluated .
TL;DR: Compared with the published MMW amplifiers, these PAs achieve high output power and wide band performances simultaneously, and the ouput power levels is the state-of-the-art performance at these frequencies.
Abstract: In this paper, we propose a design method of multi-way combining networks with impedance transformation for millimeter-wave (MMW) power amplifiers (PAs) to achieve high output power and wideband performance simultaneously in millimeter-wave frequency. Based on the proposed methodology, three power amplifiers are designed and fabricated in V-band, W-band, and D-band using 65-nm CMOS technology. With 1.2-V supply, the saturation powers of these power amplifiers are 23.2 dBm, 18 dBm and 13.2 dBm at 64 GHz, 90 GHz, and 140 GHz, with 25.1-GHz, 26-GHz, and 30-GHz 3-dB bandwidth, respectively. Compared with the published MMW amplifiers, these PAs achieve high output power and wide band performances simultaneously, and the ouput power levels is the state-of-the-art performance at these frequencies.
TL;DR: In this article, a tunable bandpass filter using cross-shaped multiple mode resonators (MMRs) and N:1 transformer based external quality factor tuning structures is proposed.
Abstract: In this paper, a tunable bandpass filter using cross-shaped multiple mode resonators (MMRs) and N:1 transformer based external quality factor tuning structures is proposed. The use of a cross-shaped MMR simplifies inter-resonators control while two Qe tuning structures are investigated and incorporated with the MMR to implement simultaneous center frequency agility and narrow and wide bandwidth tuning. Compared with traditional tunable filters, the proposed architecture requires less tuning elements and is easier to realize wideband and high-order tunable filters. Two examples (Filter I and II) are presented to validate the design. Both filters use a single MMR and six tuning elements to achieve a third-order wideband tunable filter. Filter I reports 58% center frequency tuning with constant bandwidth and 14%-64.4% fractional bandwidth (FBW) tuning when center frequency locates at 1 GHz. Filter II achieves larger frequency agility and wider FBW tuning of 82.9% and 95%, respectively, for the same bandwidth and center frequency of Filter I.
TL;DR: In this article, the authors demonstrate a high-spatial-resolution fast Brillouin optical time-domain analysis (BOTDA) for distributed dynamic strain measurement based on differential double-pulse and second-order sideband of modulation.
Abstract: We demonstrate a high-spatial-resolution fast Brillouin optical time-domain analysis (BOTDA) for distributed dynamic strain measurement based on differential double-pulse and second-order sideband of modulation. The frequency-agility probe wave is obtained from the second-order sideband of the modulated light by using the microwave signal from a wideband arbitrary waveform generator (AWG), which reduces the bandwidth requirement of the AWG by half to ~ 5.5 GHz. The differential double-pulse scheme is proposed to improve the spatial resolution while keeping the capability of dynamic measurement. In experiment, a spatial resolution of 20 cm is achieved by using a 52/50 ns differential double-pulse, and the distributed vibration measurement is demonstrated over a 50-m Panda polarization-maintaining fiber observing the vibration frequency of up to 50 Hz. With only five averages, the standard deviation of the strain accuracy is measured to be 14 μe.
TL;DR: A widely tunable optoelectronic oscillator (OEO) based on a broadband phase modulator and a tunable optical bandpass filter is proposed and experimentally demonstrated, achieving the widest fundamental frequency tunable range ever achieved by an OEO.
Abstract: A widely tunable optoelectronic oscillator (OEO) based on a broadband phase modulator and a tunable optical bandpass filter is proposed and experimentally demonstrated. A tunable range from 4.74 to 38.38 GHz is realized by directly tuning the bandwidth of the optical bandpass filter. To the best of our knowledge, this is the widest fundamental frequency tunable range ever achieved by an OEO. The phase noise performance of the generated signal is also investigated. The single-sideband phase noise is below -120 dBc/Hz at an offset of 10 KHz within the whole tunable range.
TL;DR: In this paper, a polyethylene terephthalate (PET) substrate and implemented by inkjet printing using a conductive ink, is proposed as a passive tag antenna for UHF radio frequency identification (RFID).
Abstract: A new antenna, designed on a polyethylene terephthalate (PET) substrate and implemented by inkjet printing using a conductive ink, is proposed as a passive tag antenna for UHF radio frequency identification (RFID). The operating bandwidth of the proposed antenna is very large since it encompasses all worldwide UHF RFID bands and extends well beyond at both edges. Moreover, it has a very simple geometry, can be easily tuned to feed many of the commercial RFID chips, and is very robust with respect to realization tolerances. The antenna has been designed using a general-purpose 3-D computer-aided design (CAD), CST Microwave Studio, and measured results are in very good agreement with simulations. The proposed passive RFID tag meets both the objectives of low-cost and size reduction.
TL;DR: In this paper, the simulation and experimental results of a novel wideband wearable circularly polarized textile antenna for low-power transmission in the 2.45 GHz ISM band are presented.
Abstract: In this communication, the simulation and experimental results of a novel wideband wearable circularly polarized textile antenna for low-power transmission in the 2.45 GHz ISM band are presented. The wide impedance and axial ratio bandwidths make it perfect for low microwave power transmission to a wearable sensor system. The antenna is flexible, robust and light weight so that it can be easily integrated into clothes. It is shown that the circularly polarized textile antenna has a 3-dB axial ratio bandwidth of 564 MHz (23%) and a -10dB impedance bandwidth of 1086 MHz (44%) on a human body with the maximum gain of 4.9 dBic. Lastly, the textile antenna is employed on the battery-less temperature sensor system on a human arm to demonstrate the effective power transmission over a metre distance.
TL;DR: In this article, a superstrateenhanced substrate-loaded array (SESLA) with an integrated feed is presented, which allows for a practical implementation of the SESLA, a concept previously presented by the authors for realizing extremely wideband (> 10:1) low profile arrays.
Abstract: A superstrate-enhanced substrate-loaded array (SESLA) with an integrated feed is presented. The design allows for a practical implementation of the SESLA, a concept previously presented by the authors for realizing extremely wideband (> 10:1) low-profile arrays. Specifically, the feed provides unbalanced to balanced transformation allowing the balanced-fed SESLA to be excited with a 50Ω unbalanced line. The resulting array/feed combination is matched across a 13.9:1 bandwidth (infinite array, VSWR ≤ 2.4). When scanned to 450 in the E-, H-, and D-planes, the unit cell operates across a 13.3:1 bandwidth using a relaxed matching criterion of VSWR ≤ 3. The design is validated through extensive measurement of an 8 × 8 prototype array.
TL;DR: In this paper, a wideband, wide-scan phased array of connected dipoles has been designed and fabricated, and measured results from a 77 prototype demonstrator are presented for experimental validation.
Abstract: A wideband, wide-scan phased array of connected dipoles has been designed and fabricated. Measured results from a 77 prototype demonstrator are presented for experimental validation. In order to avoid common-mode resonances that typically affect this type of array, loop-shaped transformers are included in the feed network. The common-mode rejection implemented by these transformers allow maintaining the cross-polarization levels to values lower than over a 30% relative bandwidth, for an elevation angle up to 45 in all azimuth planes. The array exhibits a measured voltage standing-wave ratio (VSWR) lower than 2.5 from 3 to 5 GHz for broadside radiation. The VSWR maintains levels lower than 3 within a scan volume of 45 from broadside in all planes.
Posted Content•
07 Feb 2013
TL;DR: In this article, various wideband spectrum sensing algorithms are presented, together with a discussion of the pros and cons of each algorithm and th e challenging issues.
Abstract: Cognitive radio has emerged as one of the most promising cand id te solutions to improve spectrum utilization in next generation cellular networks. A crucia l requirement for future cognitive radio networks is wideband spectrum sensing: secondary users reliably det ect spectral opportunities across a wide frequency range. In this article, various wideband spectru m sensing algorithms are presented, together with a discussion of the pros and cons of each algorithm and th e challenging issues. Special attention is paid to the use of sub-Nyquist techniques, including compre ssed sensing and multi-channel sub-Nyquist sampling techniques.
TL;DR: In this paper, the first use of the CW-seeded parametric comb as a multi-wavelength source for coherent channel transmitters was reported, which relies on a multistage parametric mixer design seeded by a single kilohertz-linewidth master laser.
Abstract: We report the first use of the CW-seeded parametric comb as a multiwavelength source for coherent channel transmitters. The new comb source relies on a multistage parametric mixer design seeded by a single kilohertz-linewidth master laser. The resultant frequency comb provides more than 120 tones in a 100-nm-wide continuous band, all possessing kilohertz-scale linewidth inherited from the master laser. The applicability of the new comb source as a coherent channel carrier was quantified by error-vector magnitude and bit-error rate metrics of individual spectral lines modulated by QPSK signaling. The performance of the new source exceeded that of the standard tunable coherent transmitter while providing a qualitatively lower frequency uncertainty and drift.